The present application relates generally to cleaning exhaust gas. In particular, the present application relates to the sterilization of objects using hydrogen peroxide vapor and for the decomposing of hydrogen peroxide vapor exhausted during the process. Systems are available for the sterilization of objects, such as medical instruments, utilizing hydrogen peroxide vapor to effect sterilization. In such systems, the objects are placed in a sterilization chamber and hydrogen peroxide vapor is pumped in. After the objects are sterilized, exhaust comprising hydrogen peroxide vapor is exhausted from the chamber. A need exists for reducing the concentration of hydrogen peroxide exhausted from the system.